Control Components

CONTROL COMPONENTS

ELECTRONIC MANUAL TEMPERATURE CONTROL
The electronic manual temperature control (EMTC) components are used to select:
- air inlet source (outside or recirculated).
- blower motor speed.
- discharge air temperature (temperature blend).
- discharge air location (defrost, panel, floor).
- A/C compressor operation.

Control System Inputs
The EMTC system has 2 system control inputs.

Climate Control Assembly (EMTC Module)
The climate control assembly integrates the temperature control, airflow mode selection, A/C request button, recirculated air request button and rear defog switch into a single unit.

The temperature control switch setting determines air temperature. Movement of the temperature display from COOL (blue) to WARM (red) causes corresponding movement of the temperature blend door and determines the air discharge temperature that the air distribution system will maintain. The temperature control switch is an integral part of the climate control assembly and cannot be replaced separately.

The A/C request button determines A/C compressor operation, except when the function selected is in the OFF, MAX or DEFROST mode. The A/C request button is an integral part of the climate control assembly and cannot be replaced separately.

The recirculated air request button can select recirculated air in any mode except DEFROST, and fresh air in any mode except MAX A/C or OFF.

The rear defog button signals activation of the heated backlight. The rear defog button is an integral part of the climate control assembly and cannot be installed separately.

The EMTC module is not equipped with self-test capabilities.

Blower Motor Switch
The blower motor switch is mounted in the climate control assembly and controls blower motor speed by adding or bypassing resistors in the blower motor resistor in all modes except OFF.

Control System Outputs
The EMTC system has 3 system outputs.

Blower Motor Resistor
The blower motor resistor:
- is located on the heater core and evaporator core housing near the blower motor.
- has 3 resistor elements mounted on the resistor board to provide 4 blower motor speeds.
- depending on the blower motor switch position, series resistance is added or bypassed in the blower motor circuit to decrease or increase blower motor speed.

Temperature Blend Door Actuator
The temperature blend door actuator:
- is located on the heater core and evaporator core housing.
- moves the temperature blend door on command from the EMTC module.
- contains a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the temperature blend door.
- applies a 5-volt signal to one end of the potentiometer and ground to the other. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the EMTC module and is matched with an expected wiper voltage value. The EMTC module then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the expected EMTC module wiper voltage value.

Mode Door Actuator
The mode door actuator:
- uses a cam setup to direct system airflow to the vehicle interior as determined by the climate control assembly.
- contains a reversible electric motor.
- contains a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the mode door.
- applies a 5-volt signal to one end of the potentiometer and ground to the other. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the EMTC module and is matched with an expected wiper voltage value. The EMTC module then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the expected EMTC module wiper voltage value.

Air Inlet Mode Door Actuator
The air inlet mode door actuator:
- moves the air inlet door between the FRESH and RECIRC positions on command from the EMTC module.
- contains a reversible electric motor.
- automatically stops when it reaches the full FRESH or full RECIRC position and does not report its position back to the EMTC module.

ELECTRONIC AUTOMATIC TEMPERATURE CONTROL
Two different electronic automatic temperature control systems are available:
- Single-zone EATC (Fusion/Milan)
- Dual-zone EATC (Zephyr)

The electronic automatic temperature control (EATC) module analyzes input from the following major sources:
- Temperature, airflow direction, blower, A/C and RECIRC selection (made by the vehicle occupants)
- In-vehicle temperature sensor
- Ambient temperature sensor
- Solar radiation sensor
- Vehicle speed
- Engine coolant temperature

Using these inputs, the dual-zone EATC module determines the correct conditions for the following outputs:
- A/C compressor operation
- Blower speed
- Temperature blend door position
- DEFROST/PANEL/FLOOR door position
- Air inlet door position

Control System Inputs
The dual-zone EATC system has 4 control system inputs.

EATC Module
The dual-zone EATC module:
- is located in the instrument panel.
- has a vacuum fluorescent display for displaying set temperature, airflow direction, blower speed and diagnostic trouble codes (DTCs).
- utilizes an on-board diagnostic (OBD) feature to supply the technician with diagnostic trouble codes (DTCs). These DTCs direct the technician to the inoperative component.

In-Vehicle Temperature Sensor
The in-vehicle temperature sensor operates in the following manner:
- A thermistor in the in-vehicle temperature sensor measures air temperature inside the passenger compartment.
- An aspirator hose and elbow is connected between the heater core and evaporator core housing and the in-vehicle temperature sensor.
- The aspirator hose and elbow takes air from the heater core and evaporator core housing air stream to create a suction in the in-vehicle temperature sensor.
- The suction draws in-vehicle air into the in-vehicle temperature sensor and across the thermistor.

Solar Radiation Sensor (Sunload Sensor)
The solar radiation sensor supplies information to the EATC module indicating sunload.

Ambient Temperature Sensor
The ambient temperature sensor signal is received by the EATC module and indicates the outside air temperature. The ambient temperature sensor is located in front of the radiator on the radiator support.

Control System Outputs
The EATC system has 3 control system outputs.

Blower Motor Speed Control
The blower speed control:
- is located on the heater core and evaporator core housing near the blower motor.
- varies the blower motor speed and is controlled by the EATC module software.

Temperature Blend Door Actuator(s)
Single-zone EATC systems use one temperature blend door actuator. Dual-zone EATC systems use 2 separate temperature blend door actuators to control 2 separate temperature blend doors for the driver and passenger sides of the vehicle. The temperature blend door actuator(s):
- is/are located on the heater core and evaporator core housing.
- move the temperature blend door(s) on command from the dual-zone EATC module.
- each contain a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the temperature blend doors.

A 5-volt signal is applied to one end of the potentiometer and ground to the other. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the EATC module and is matched with an expected wiper voltage value. The EATC module then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the expected EATC module wiper voltage value.

Mode Door Actuator
The mode door actuator:
- uses a cam setup to position the 2 airflow mode doors to direct system airflow to the vehicle interior as determined by the EATC module settings.
- contains a reversible electric motor.
- contains a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate the position of the mode door.

A 5-volt signal is applied to one end of the potentiometer and ground to the other. The voltage available at the wiper indicates the position of the potentiometer. The expressed value of the actuator wiper voltage is sent to the EATC module and is matched with an expected wiper voltage value. The EATC module then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the expected EATC module wiper voltage value.

Air Inlet Mode Door Actuator
The air inlet mode door actuator:
- moves the air inlet door between the FRESH and RECIRC positions on command from the EATC module.
- contains a reversible electric motor.
- automatically stops when it reaches the full FRESH or full RECIRC position and does not report its position back to the EATC module.